The main thrust of the research is to ascertain the effects of air pollutant gases on lung development and to determine whether growth is impaired after exposure to concentrations of pollutants at levels similar to those noted for urban environments. The objectives are 1) to characterize and quantify the growth and development of residual lung tissue in animals following pneumonectomy, 2) to expose pneumonectomized animals to single or multiple concentrations of a common air pollutant ozone (and possibly SO2 or NO2) and 3) to determine if, and to what extent, growth of the residual lung is impaired by exposure to the gas and the factors responsible for this impairment.